Tips for low-grade iron ore beneficiation

I. Process Background and Challenges

The development and utilization of low - grade iron ores, which are characterized by low iron content, complex composition, and fine - grained minerals, is crucial for alleviating the shortage of iron ore resources. There are three major challenges in the beneficiation of such ores:

Complex Composition: Impurities such as sulfur, phosphorus, and silicon coexist with iron minerals, affecting the separation efficiency and the quality of smelting products.

Fine - grained Particles: Fine - grained iron ores, such as hematite, are often enclosed in gangue, resulting in low recovery rates with traditional beneficiation processes.

Limited Resources: The ore bodies are scattered and the processing volume is large, necessitating technological innovation to improve resource utilization rates.

II. Core Beneficiation Process Methods

1. Optimization of Magnetic Separation: Precise Separation of Weakly Magnetic Minerals

High - precision Magnetic Separation Equipment:
Superconducting magnetic separators or high - gradient magnetic separators are employed, with the magnetic field strength increased to 1.5 - 2.0T, effectively capturing fine (<30μm) weakly magnetic iron ore particles.

Pretreatment Processes:

• Multi - stage Crushing and Classification: The ore is crushed to 0.1 - 1mm by high - pressure grinding rolls, and then classified by hydrocyclones to optimize the particle size distribution.

• Magnetizing Roasting: Hematite is subjected to reduction roasting at 600 - 800℃, which is transformed into strongly magnetic magnetite, and the magnetic separation recovery rate is increased to over 85%.

Parameter Optimization:
The magnetic field strength, separation gap (5 - 10mm), and drum rotation speed (200 - 400r/min) are adjusted dynamically to adapt to different ore phase characteristics.

2. Innovation in Flotation: Efficient Separation of Complex Minerals

New Flotation Reagents:

• Composite Collector: Dodecylamine is compounded with oxidized paraffin soap at a ratio of 1:3, which selectively adsorbs iron minerals, and the inhibition rate of siliceous gangue is increased by 40%.

• Environment - friendly Inhibitor: Modified starch replaces traditional cyanides, reducing toxicity and enhancing the separation effect between hematite and quartz.

Micro - bubble Flotation Technology:
A nano - bubble generator (with a bubble diameter <50μm) is used to increase the contact probability between ore particles and bubbles, and the recovery rate of fine - grained iron ores is increased to 75%.

Application of Column Flotation Machines:
By optimizing the pulp concentration (25 - 35%), pH value (8 - 9), and air - inflow, continuous and efficient separation is achieved, and the concentrate grade reaches over 62%.

3. Development of Combined Processes: Synergistic Enhancement and Comprehensive Resource Utilization

Combined Magnetic Separation - Flotation Process:

• Pre - magnetic Separation: More than 80% of magnetic gangue is removed, reducing the flotation treatment volume.

• Reverse Flotation for Silica Removal: Anionic collectors (such as MH - 88) are used to preferentially float silicates in an alkaline environment, and the grade of iron concentrate is increased to 65%.

Combined Recovery Process for Fine - grained Ores:

• High - intensity Magnetic - Centrifugal Gravity Separation: High - gradient magnetic separation is carried out on the slime (<0.038mm), and then enrichment is carried out by a centrifuge, increasing the recovery rate by 20%.

• Selective Flocculation - Flotation: Polyacrylamide flocculant is added to agglomerate fine - grained iron minerals, and then separation is carried out by flotation, reducing the iron content in the tailings to less than 8%.

Intelligent Process Control:
Machine - learning models are used to analyze the ore composition (XRF/XRD data) in real - time, and the separation parameters are adjusted dynamically, enhancing the process stability by 30%.